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List: xen-users
Subject: Re: [Xen-users] Massive iowait with Xen 3.2
From: Antoine Benkemoun <antoine.benkemoun () gmail ! com>
Date: 2009-04-30 8:51:50
Message-ID: fc1cbedb0904300151q4b26e6d7h84ab26df0f3e7a1d () mail ! gmail ! com
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Thank you all for your answers.
I'm taking good note of the fact that this is most likely tied to the fact
to BT is IO intensive and that I need more RAM. That will teach me to leave
some room for dom0 :-)
On Wed, Apr 29, 2009 at 8:15 PM, Christopher Chen <muffaleta@gmail.com>wrote:
> Also, if you're using file: vbd access, and you're low on ram, I
> imagine your buffer cache on the dom0 is nearly nonexistent, which
> would kill any writes.
>
> You might want to get more RAM while you're at it.
>
> On Tue, Apr 28, 2009 at 6:20 AM, Fajar A. Nugraha <fajar@fajar.net> wrote:
> > On Tue, Apr 28, 2009 at 7:59 PM, Antoine Benkemoun
> > <antoine.benkemoun@gmail.com> wrote:
> > > Thank you for your answer. Sorry for the headers !
> > >
> > > 4MB/s read speed is just plain ridiculous for a hard drive or is it just
> me
> > > ?
> >
> > I don't think its the transfer rate. Its the IOPS thats causing your
> problems.
> > This link (from Googling "one disk iops")
> >
> http://forums11.itrc.hp.com/service/forums/questionanswer.do?admit=109447626+1240923773781+28353475&threadId=1122630
>
> > indicates max IOPS for one disk is lower then your current numbers
> > (180). So I guess you're IOPS bound. Adding more disk with the right
> > setup would increase the number of IOPS you can handle.
> >
> > Since the IOPS are mostly read, you MIGHT be able to reduce it by
> > giving domU more RAM, enough to hold the torrent it's running. So
> > instead of having 8 domUs with 256 MB each, try using only 1 or 2
> > domUs with 1 GB memory.
> >
> > > These domains are actually stored on LVM so that's already in place but
> > > iostat doesn't seem to differenciate...
> >
> > Weird. I swear in shows up on RHEL. Could be they have vendor-specific
> > patch. What does /proc/partitions and /proc/diskstats show, does it
> > have "dm" entries?
> >
> > Anyway, from the output of "xm top" you should also be able to
> > determine which domU uses most I/O (look in VBD_RD column). In general
> > bittorrent IS very I/O intensive. If you want to limit the amount of
> > I/O a domU can use (so that whatever they do they never made the
> > entire system crawl down), you might be interested in dm-ioband.
> > Haven't used it myself, but it looks good.
> > http://people.valinux.co.jp/~ryov/dm-ioband/<http://people.valinux.co.jp/%7Eryov/dm-ioband/>
> >
> > Regards,
> >
> > Fajar
> >
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@lists.xensource.com
> > http://lists.xensource.com/xen-users
> >
>
>
>
> --
> Chris Chen <muffaleta@gmail.com>
> "I want the kind of six pack you can't drink."
> -- Micah
>
[Attachment #5 (text/html)]
Thank you all for your answers.<br><br>I'm taking good note of the fact that this \
is most likely tied to the fact to BT is IO intensive and that I need more RAM. That \
will teach me to leave some room for dom0 :-)<br><br> <div class="gmail_quote">On \
Wed, Apr 29, 2009 at 8:15 PM, Christopher Chen <span dir="ltr"><<a \
href="mailto:muffaleta@gmail.com">muffaleta@gmail.com</a>></span> \
wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, \
204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Also, if you're using file: \
vbd access, and you're low on ram, I<br> imagine your buffer cache on the dom0 is \
nearly nonexistent, which<br> would kill any writes.<br>
<br>
You might want to get more RAM while you're at it.<br>
<div><div></div><div class="h5"><br>
On Tue, Apr 28, 2009 at 6:20 AM, Fajar A. Nugraha <<a \
href="mailto:fajar@fajar.net">fajar@fajar.net</a>> wrote:<br> > On Tue, Apr 28, \
2009 at 7:59 PM, Antoine Benkemoun<br> > <<a \
href="mailto:antoine.benkemoun@gmail.com">antoine.benkemoun@gmail.com</a>> \
wrote:<br> >> Thank you for your answer. Sorry for the headers !<br>
>><br>
>> 4MB/s read speed is just plain ridiculous for a hard drive or is it just \
me<br> >> ?<br>
><br>
> I don't think its the transfer rate. Its the IOPS thats causing your \
problems.<br> > This link (from Googling "one disk iops")<br>
> <a href="http://forums11.itrc.hp.com/service/forums/questionanswer.do?admit=109447626+1240923773781+28353475&threadId=1122630" \
target="_blank">http://forums11.itrc.hp.com/service/forums/questionanswer.do?admit=109447626+1240923773781+28353475&threadId=1122630</a><br>
> indicates max IOPS for one disk is lower then your current numbers<br>
> (180). So I guess you're IOPS bound. Adding more disk with the right<br>
> setup would increase the number of IOPS you can handle.<br>
><br>
> Since the IOPS are mostly read, you MIGHT be able to reduce it by<br>
> giving domU more RAM, enough to hold the torrent it's running. So<br>
> instead of having 8 domUs with 256 MB each, try using only 1 or 2<br>
> domUs with 1 GB memory.<br>
><br>
>> These domains are actually stored on LVM so that's already in place \
but<br> >> iostat doesn't seem to differenciate...<br>
><br>
> Weird. I swear in shows up on RHEL. Could be they have vendor-specific<br>
> patch. What does /proc/partitions and /proc/diskstats show, does it<br>
> have "dm" entries?<br>
><br>
> Anyway, from the output of "xm top" you should also be able to<br>
> determine which domU uses most I/O (look in VBD_RD column). In general<br>
> bittorrent IS very I/O intensive. If you want to limit the amount of<br>
> I/O a domU can use (so that whatever they do they never made the<br>
> entire system crawl down), you might be interested in dm-ioband.<br>
> Haven't used it myself, but it looks good.<br>
> <a href="http://people.valinux.co.jp/%7Eryov/dm-ioband/" \
target="_blank">http://people.valinux.co.jp/~ryov/dm-ioband/</a><br> ><br>
> Regards,<br>
><br>
> Fajar<br>
><br>
</div></div>> _______________________________________________<br>
> Xen-users mailing list<br>
> <a href="mailto:Xen-users@lists.xensource.com">Xen-users@lists.xensource.com</a><br>
> <a href="http://lists.xensource.com/xen-users" \
target="_blank">http://lists.xensource.com/xen-users</a><br> ><br>
<font color="#888888"><br>
<br>
<br>
--<br>
Chris Chen <<a href="mailto:muffaleta@gmail.com">muffaleta@gmail.com</a>><br>
"I want the kind of six pack you can't drink."<br>
-- Micah<br>
</font></blockquote></div><br>
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